It is known to provide large cars and the like with central door-lock systems. Such a system normally is connected to the door lock of the driver's door so that when this door is locked or unlocked all of the other door locks of the vehicle are simultaneously operated. This system is particularly convenient in a large vehicle where it is very difficult for the driver to reach back or across to open any of the other doors.
Such systems normally use standard door latches, each of which normally has a detent lockingly engageable with a bolt or pin on the respective doorpost and displaceable between and open and closed position allowing the door to be separated from the respective doorpost or securely holding the door to its respective doorpost. Mechanism inside the lock allows this detent to be operated by inside and outside door handles, and this mechanism itself is normally controlled by inside and outside door locks that allow the inside and outside door handles to be uncoupled from the detent. Thus when the door is locked it cannot be opened from either the inside or outside handle, and this locking can be carried out either by means of an externally accessible key-operated door lock or by means of an internal door button or lever. Each such latch is associated with a respective servo-actuator that in the simplest instance is a double-acting solenoid coupled to the inside door-lock button and operable from the driver's position to lock and unlock the doors.
Such systems do not, however, normally offer any additional security against breaking-into or theft of the motor vehicle. Thus it is possible for a burglar to simply smash or pry open a window, then reach in and unlock the respective door by means of the respective inside door-lock button or lever. The fact that the vehicle is equipped with a central lock system is irrelevant in such a situation.
Although it has been suggested to incorporate some particular precautions in a central locking system to discourage theft, such arrangements normally have added substantially to the cost of the system. What is more such arrangements normally require the standard door latches of a motor vehicle to be entirely rebuilt or replaced with special ones that work together with the new antitheft means. Such an arrangement can be seen from my copending application Ser. No. 132,977, whose entire disclosure is herewith incorporated by reference.